Agonizing Beam of Force

Choose a creature within range. As you extend your pointer you expel a massive beam of force. The creature must make a dexterity saving throw or take 35 (10d6) force damage on a failure and is stunned on a success the creature takes half damage and isn't stunned. If you have taken damage in the past round then you can increase the damage by 3d6 for every 20 damage you have received.